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Adding & subtracting like fractions

Fractions

Japanese school year: Elementary 3

What you learn

You will learn how to add and subtract fractions sharing identical denominators by operating only on their numerators. This is practical when combining or removing parts measured with the same unit fraction. Understanding that fractions represent collections of unit parts will make this concept very intuitive.

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Key points

This formula is used to add fractions that share the same denominator cc. Keep the denominator cc as it is, and add the numerators aa and bb together.

ac+bc=a+bc\frac{a}{c} + \frac{b}{c} = \frac{a + b}{c}

This formula is used to subtract fractions that share the same denominator cc. Keep the denominator cc as it is, and subtract numerator bb from aa.

ac−bc=a−bc\frac{a}{c} - \frac{b}{c} = \frac{a - b}{c}

This is the rule for simplifying fractions after calculation (reducing fractions). When both the numerator and denominator share a common factor, divide them to express the fraction in its simplest form.

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